Comparison of the Effects of Botulinum Toxin Doses on Nerve Regeneration in Rats with Experimentally Induced Sciatic Nerve Injury.

This study was designed to compare the effects of various doses of botulinum neurotoxin A (BoNT/A) on nerve regeneration. Sixty-five six-week-old rats with sciatic nerve injury were randomly allocated to three experimental groups, a control group, and a sham group. The experimental groups received a single session of intraneural BoNT/A (3.5, 7.0, or 14 U/kg) injection immediately after nerve-crushing injury. The control group received normal intraneural saline injections after sciatic nerve injury. At three, six, and nine weeks after nerve damage, immunofluorescence staining, an ELISA, and toluidine blue staining was used to evaluate the regenerated nerves. Serial sciatic functional index analyses and electrophysiological tests were performed every week for nine weeks. A higher expression of GFAP, S100ß, GAP43, NF200, BDNF, and NGF was seen in the 3.5 U/kg and 7.0 U/kg BoNT/A groups. The average area and myelin thickness were significantly greater in the 3.5 U/kg and 7.0 U/kg BoNT/A groups. The sciatic functional index and compound muscle action potential amplitudes exhibited similar trends. These findings indicate that the 3.5 U/kg and 7.0 U/kg BoNT/A groups exhibited better nerve regeneration than the 14 U/kg BoNT/A and control group. As the 3.5 U/kg and the 7.0 U/kg BoNT/A groups exhibited no statistical difference, we recommend using 3.5 U/kg BoNT/A for its cost-effectiveness.

Risk of Neurodegenerative Diseases in Elderly Koreans with an Initial Diagnosis of Type 2 Diabetes: A Nationwide Retrospective Cohort Study.

Type 2 diabetes (T2D) and neurodegenerative diseases (NDs) are common among elderly individuals. Growing evidence has indicated a strong link between T2D and NDs, such as Alzheimer's disease. However, previous studies have limitations in exploring the epidemiological relationship among these diseases as a group of NDs rather than as a specific type of ND. We aimed to investigate the risk of NDs in elderly Koreans who were first diagnosed with T2D and determine the association between T2D and NDs. We conducted a retrospective longitudinal cohort study of patients with who were initially diagnosed with T2D using the Korean National Health Information Database. The study participants were categorized into a T2D group (n = 155,459) and a control group (n = 155,459), aged 60-84 years, that were matched for age, sex, and comorbidities. We followed the participants for 10 years to investigate the incidence of NDs. The Cox proportional hazards regression model was used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) for NDs. The numbers of patients diagnosed with ND at the end of follow-up were as follows: 51,096/155,459 (32.9%) in the T2D group and 44,673/155,459 (28.7%) in the control group (χ2 = 622.53, p < 0.001). The incidences of NDs in the T2D and control groups were 44.68 (95% CI: 44.29, 45.07) and 36.89 (95% CI: 36.55, 37.24) cases per 1,000 person-years at risk, respectively. The overall incidence of NDs was higher in the T2D group than that in the control group (HR: 1.23, 95% CI: 1.22, 1.25, p < 0.001). This study revealed a higher incidence of NDs in elderly Koreans who were initially diagnosed with T2D. This suggests that T2D is a risk factor for NDs in elderly Koreans.

Fast Water Transport in UTSA-280 via a Knock-Off Mechanism.

Water and other small molecules frequently coordinate within metal-organic frameworks (MOFs). These coordinated molecules may actively engage in mass transfer, moving together with the transport molecules, but this phenomenon has yet to be examined. In this study, we explore a unique water transfer mechanism in UTSA-280, where an incoming water molecule can displace a coordinated molecule for mass transfer. We refer to this process as the "knock-off" mechanism. Despite UTSA-280 possessing one-dimensional channels, the knock-off transport enables water movement along the other two axes, effectively simulating a pseudo-three-dimensional mass transfer. Even with a relatively narrow pore width, the knock-off mechanism enables a high water flux in the UTSA-280 membrane. The knock-off mechanism also renders UTSA-280 superior water/ethanol diffusion selectivity for pervaporation. To validate this unique mechanism, we conducted 1 H and 2 H solid-state NMR on UTSA-280 after the adsorption of deuterated water. We also derived potential energy diagrams from the density functional theory to gain atomic-level insight into the knock-off and the direct-hopping mechanisms. The simulation findings reveal that the energy barrier of the knock-off mechanism is marginally lower than the direct-hopping pathway, implying its potential role in enhancing water diffusion in UTSA-280.

Trends in concomitant and single opioid and benzodiazepine exposures reported to the California Poison Control System following the Centers for Disease Control and Prevention release of opioid guidelines in 2016.

INTRODUCTION: In March 2016, the Centers for Disease Control and Prevention released the Guideline for Prescribing Opioids for Chronic Pain, intended for primary care clinicians. One recommendation advised against concurrent prescription of opioids and benzodiazepines. Although existing research suggests a reduction in co-prescribing of these drug classes by clinicians after guideline release, there are limited data assessing its possible effect on patient medical outcomes, such as overdoses. METHODS: This retrospective observational study analyzed opioid and benzodiazepine exposures, alone or in combination, reported to the California Poison Control System from January 2012 to June 2021. Interrupted time series analyses identified the difference in monthly call volume between pre- and post-guideline release. For exposures resulting in serious medical outcomes, additional analyses assessed trends and identified associated variables. RESULTS: There was no significant change in concomitant opioid and benzodiazepine exposures reported to California Poison Control System between pre- and post-guideline release. Compared to pre-guideline release, exposures to a single opioid or to a single benzodiazepine significantly decreased by 1.07 (95% CI: -1.62, -0.51) and 1.82 (95% CI: -2.33, -1.31) calls per month, respectively, after the guideline release. For exposure calls associated with serious medical outcomes, there was a significant increase of 0.11 (95% CI: 0.04, 0.18) and 0.2 (95% CI: 0.05, 0.34) calls per month for concomitant opioid and benzodiazepine and single opioid exposures, respectively, following guideline release. DISCUSSION: The guideline release appeared to have a variable association with exposures to single opioid, single benzodiazepines, and concomitant opioid and benzodiazepine cases reported to California Poison Control System. Although exposures to opioids or benzodiazepines alone significantly decreased after guideline release, there was no significant change in concomitant exposures. Additionally, for exposures associated with serious medical outcomes, concomitant exposures, and single opioid exposures significantly increased following guideline release. CONCLUSION: Our results suggest that the guideline was not associated with a corresponding decrease in the number of concomitant poisoning exposures reported to California Poison Control System. Additional interventions may be needed to reduce concomitant exposures to opioids and benzodiazepines.

A Van Der Waals Reconfigurable Multi-Valued Logic Device and Circuit Based on Tunable Negative-Differential-Resistance Phenomenon.

Multi-valued logic (MVL) technology that utilizes more than two logic states has recently been reconsidered because of the demand for greater power saving in current binary logic systems. Extensive efforts have been invested in developing MVL devices with multiple threshold voltages by adopting negative differential transconductance and resistance. In this study, a reconfigurable, multiple negative-differential-resistance (m-NDR) device with an electric-field-induced tunability of multiple threshold voltages is reported, which comprises a BP/ReS2 heterojunction and a ReS2 /h-BN/metal capacitor. Tunability for the m-NDR phenomenon is achieved via the resistance modulation of the ReS2 layer by electrical pulses applied to the capacitor region. Reconfigurability is verified in terms of the function of an MVL circuit composed of a reconfigurable m-NDR device and a load transistor, wherein staggered-type and broken-type double peak-NDR device operations are adopted for ternary inverter and latch circuits, respectively.

Treatment Outcomes of Sinonasal Malignancies Involving the Orbit.

Objective Orbital invasion is associated with a poor prognosis in cases of sinonasal malignancy. This study aimed to analyze the oncological outcomes of sinonasal malignancies involving the orbit. Patients and Methods We reviewed the medical records of 116 patients with a sinonasal malignancy who had orbital invasion at initial diagnosis and followed up at least 6 months between June 1991 and October 2017 at a single institute. The overall survival (OS), disease-specific survival (DSS), and progression-free survival (PFS) rates according to the clinicopathological factors, extent to orbit, and treatment modality were compared. Results Patients were mainly treated with surgery and postoperative radiation ( n = 39, 33.6%) and concurrent chemoradiation ( n = 72, 62.1%). Only five patients (5.1%) underwent orbital exenteration. The OS, DSS, and PFS rates significantly decreased in patients older than 60 years of age and in patients with a higher Charlson Comorbidity Index Score (each p < 0.001). The OS and DSS rates were higher in patients at clinical T3 and N0 stage than in patients at clinical T4 and N1-2 stage (each p < 0.05). There were no significant differences in survival and local control rates according to the extent of orbital invasion, treatment modalities, and orbital preservation. However, neoadjuvant chemotherapy and adjuvant radiation or concurrent chemoradiation increased survival rates in the patients treated with surgery. Conclusion Orbit preservation and relatively successful oncological outcome could be obtained with surgery and adjuvant radiation or concurrent chemoradiation.

Microfluidic Screening-Assisted Machine Learning to Investigate Vertical Phase Separation of Small Molecule:Polymer Blend.

Solution-based thin-film processing is a widely utilized technique for the fabrication of various devices. In particular, the tunability of the ink composition and coating condition allows precise control of thin-film properties and device performance. Despite the advantage of having such tunability, the sheer number of possible combinations of experimental parameters render it infeasible to efficiently optimize device performance and analyze the correlation between experimental parameters and device performance. In this work, a microfluidic screening-embedded thin-film processing technique is developed, through which thin-films of varying ratios of small molecule semiconductor:polymer blend are simultaneously generated and screened in a time- and resource-efficient manner. Moreover, utilizing the thin-films of varying combinations of experimental parameters, machine learning models are trained to predict the transistor performance. Gaussian Process Regression (GPR) algorithms tuned by Bayesian optimization shows the best predictive accuracy amongst the trained models, which enables narrowing down of the combinations of experimental parameters and investigation of the degree of vertical phase separation under the predicted parameter space. The technique can serve as a guideline for elucidating the underlying complex parameter-property-performance correlations in solution-based thin-film processing, thereby accelerating the optimization of various thin-film devices in the future.

Structural evidence for visual arrestin priming via complexation of phosphoinositols.

Visual arrestin (Arr1) terminates rhodopsin signaling by blocking its interaction with transducin. To do this, Arr1 translocates from the inner to the outer segment of photoreceptors upon light stimulation. Mounting evidence indicates that inositol phosphates (InsPs) affect Arr1 activity, but the Arr1-InsP molecular interaction remains poorly defined. We report the structure of bovine Arr1 in a ligand-free state featuring a near-complete model of the previously unresolved C-tail, which plays a crucial role in regulating Arr1 activity. InsPs bind to the N-domain basic patch thus displacing the C-tail, suggesting that they prime Arr1 for interaction with rhodopsin and help direct Arr1 translocation. These structures exhibit intact polar cores, suggesting that C-tail removal by InsP binding is insufficient to activate Arr1. These results show how Arr1 activity can be controlled by endogenous InsPs in molecular detail.

Hypochlorous Acid Versus Saline Nasal Irrigation in Allergic Rhinitis: A Multicenter, Randomized, Double-Blind, Placebo-controlled Study.

BACKGROUND: Low concentrations of hypochlorous acid (HOCl) have proven antipruritic, anti-inflammatory, and antimicrobial effects without toxicity, although the mechanism has not been fully elucidated. OBJECTIVE: The aim of this study was to evaluate the effectiveness of HOCl nasal irrigation to reduce allergic rhinitis (AR) symptoms compared with saline nasal irrigation. METHODS: This was multicenter, randomized, double-blind, placebo-controlled study. Initially, 139 patients with perennial AR were enrolled; however, 25 did not successfully complete the study. Patients were randomly assigned to the nasal irrigation with low-concentration HOCl (n = 55) or normal saline (n = 59) treatment groups for the 4-week study period. Participants completed the Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) at every visit (baseline, Weeks 2 and 4), and Total Nasal Symptom Score (TNSS) was determined before and after nasal irrigation every morning and evening. RESULTS: We found that RQLQ scores significantly decreased after 4 weeks in the HOCl and placebo groups, but the decrement of the RQLQ score was similar between the 2 groups. Additionally, TNSS improved in both groups between baseline and Week 4, whereas there were no significant differences in the change of TNSS between the 2 groups. The HOCl group did not show any clinical side effects related to nasal irrigation. CONCLUSION: Allergic symptoms significantly decreased with low-concentration HOCl nasal irrigation, without significant adverse events. However, HOCl showed no additional improvement in symptoms compared with saline nasal irrigation for patients with perennial AR.

Efficacy of Electromechanically-Assisted Rehabilitation of Upper Limb Function in Post-Stroke Patients: A Randomized Controlled Study.

OBJECTIVE: To investigate the efficacy of electromechanically-assisted rehabilitation of upper limb function in post-stroke patients. DESIGN: Randomized controlled trial. SUBJECTS: Forty-eight stroke patients. METHODS: Patients were randomly assigned to control and experimental groups. The control group underwent occupational therapy training with conventional methods. The experimental group underwent electromechanically-assisted training using an end effector robot (Camillo®). Interventions were provided for 30 min per day, 5 days a week, for 4 weeks. Primary outcome was change in Fugl-Meyer Assessment (FMA) before and after training. Secondary outcomes were changes in hand function, upper limb strength, spasticity, mental status and quality of life. RESULTS: Mean improvement in FMA was 1.17 (standard deviation (SD) 4.18) in the control group and 2.52 (SD 5.48) in the experimental group. Although FMA in the experimental group improved significantly after training, the improvement in FMA did not differ significantly between groups. Among the secondary outcomes, the Motricity Index (MI) improved significantly after training in the experimental group, and the change in MI between groups was statistically significant. CONCLUSION: Electromechanically-assisted rehabilitation using Camillo® was not more effective than conventional occupation therapy for upper arm function.

Non-Equilibrium Sodiation Pathway of CuSbS2.

Binary metal sulfides have been explored as sodium storage materials owing to their high theoretical capacity and high stable cyclability. Nevertheless, their relative high charge voltage and relatively low practical capacity make them less attractive as an anode material. To resolve the problem, addition of alloying elements is considerable. Copper antimony sulfide is investigated as a representative case. In this study, we do not only perform electrochemical characterization on CuSbS2, but also investigate its nonequilibrium sodiation pathway employing in-/ex situ transmission electron microscopy, in situ X-ray diffraction, and density functional theory calculations. Our finding provides valuable insights on sodium storage into ternary metal sulfide including an alloying element.

An Optogenetics-Inspired Flexible van der Waals Optoelectronic Synapse and its Application to a Convolutional Neural Network.

Optogenetics refers to a technique that uses light to modulate neuronal activity with a high spatiotemporal resolution, which enables the manipulation of learning and memory functions in the human brain. This strategy of controlling neuronal activity using light can be applied for the development of intelligent systems, including neuromorphic and in-memory computing systems. Herein, a flexible van der Waals (vdW) optoelectronic synapse is reported, which is a core component of optogenetics-inspired intelligent systems. This synapse is fabricated on 2D vdW layered rhenium disulfide (ReS2 ) that features an inherent photosensitive memory nature derived from the persistent photoconductivity (PPC) effect, successfully mimicking the dynamics of biological synapses. Based on first-principles calculations, the PPC effect is identified to originate from sulfur vacancies in ReS2 that have an inherent tendency to form shallow defect states near the conduction band edges and under optical excitation lead to large lattice relaxation. Finally, the feasibility of applying the synapses in optogenetics-inspired intelligent systems is demonstrated via training and inference tasks for the CIFAR-10 dataset using a convolutional neural network composed of vdW optoelectronic synapse devices.

SSD-EMB: An Improved SSD Using Enhanced Feature Map Block for Object Detection.

The development of deep learning has achieved great success in object detection, but small object detection is still a difficult and challenging task in computer vision. To address the problem, we propose an improved single-shot multibox detector (SSD) using enhanced feature map blocks (SSD-EMB). The enhanced feature map block (EMB) consists of attention stream and feature map concatenation stream. The attention stream allows the proposed model to focus on the object regions rather than background owing to channel averaging and the effectiveness of the normalization. The feature map concatenation stream provides additional semantic information to the model without degrading the detection speed. By combining the output of these two streams, the enhanced feature map, which improves the detection of a small object, is generated. Experimental results show that the proposed model has high accuracy in small object detection. The proposed model not only achieves good detection accuracy, but also has a good detection speed. The SSD-EMB achieved a mean average precision (mAP) of 80.4% on the PASCAL VOC 2007 dataset at 30 frames per second on an RTX 2080Ti graphics processing unit, an mAP of 79.9% on the VOC 2012 dataset, and an mAP of 26.6% on the MS COCO dataset.

Validation of functional liver imaging scores (FLIS) derived from gadoxetic acid-enhanced MRI in patients with chronic liver disease and liver cirrhosis: the relationship between Child-Pugh score and FLIS.

OBJECTIVES: To validate the functional liver imaging score (FLIS) for prediction of hepatic function in gadoxetic acid-enhanced MRI. METHODS: We retrospectively identified 134 patients (88 men, 46 women; mean age, 58.8 years) between January 2015 and December 2018 with the following inclusion criteria: patients diagnosed with liver cirrhosis or chronic liver disease (CLD) who underwent gadoxetic acid-enhanced MRI. Three parameters on hepatobiliary phase images were evaluated for FLIS: liver parenchymal enhancement, biliary excretion, and signal intensity of the portal vein. Patients were classified as CLD (n = 11), Child-Pugh (CP) class A (n = 87), CP B (n = 22), or CP C (n = 14). We assessed the correlation between CP score and both FLIS and its components using Spearman rank correlation. Receiver operating characteristic (ROC) curve analysis was performed to demonstrate the cutoff value of FLIS for differentiating between CP classes. The associations between patient characteristics, serum markers, FLIS, and hepatic decompensation were evaluated with Cox proportional hazard models. RESULTS: FLIS and three FLIS parameters showed strong to very strong correlation with CP score (r = -0.60 to 0.82). ROC curve analysis showed that FLIS ≥ 5 was the optimal cutoff for prediction of CP class A or CLD (sensitivity, 83.7%; specificity, 94.4%; area under the curve [AUC], 0.93). FLIS < 5 was independently associated with the development of first hepatic decompensation in patients with CP A (HR, 50.0; 95% confidence interval, 6.2, 400.4). CONCLUSION: FLIS showed a strong correlation with hepatic function and can stratify the CP class. In addition, FLIS can help prediction for the development of first decompensation. KEY POINTS: • Functional liver imaging scores (FLIS) and its three parameters, derived from hepatobiliary phase image, have strong to very strong correlations with Child-Pugh (CP) scores. • FLIS can stratify patients with chronic liver disease or liver cirrhosis according to CP classification. • Low FLIS is an independent predictor for first hepatic decompensation in patients with CP class A.

Dorsal Augmentation Using Crushed Autologous Costal Cartilage in Rhinoplasty.

OBJECTIVE/HYPOTHESIS: For dorsal augmentation in rhinoplasty, autologous costal cartilage can be used in many different forms, including its crushed form. While only few studies have reported the outcome of dorsal augmentation using the crushed autologous costal cartilage, the current study aims to evaluate the outcome of such usage. STUDY DESIGN: Retrospective chart review. METHODS: The records of 38 patients were reviewed retrospectively. The study period was from 2006 to 2016. All enrolled patients underwent rhinoplasty that includes dorsal augmentation using crushed autologous costal cartilage. Three facial plastic surgeons evaluated the outcome using pre- and postoperative facial photographs. Patients' satisfaction was also analyzed. Anthropometric measurement was performed, and postoperative complications were investigated. RESULTS: Our cohort included 19 primary and 19 revision cases. The mean age of the patients was 31.0 years. Mean postoperative follow-up period was 36.1 months. According to facial plastic surgeons' evaluation, excellent, good, fair, poor aesthetic outcomes were achieved in 15 (39.5%), 18 (47.4%), 5 (13.1%), 0 (0.0%) cases, respectively. Patients were very satisfied, satisfied, moderate, dissatisfied in 16 (42.1%), 15 (39.5%), 6 (15.8%), 1 (2.6%) cases, respectively. Heights of the dorsum and radix were significantly increased after surgery (for each, p < 0.05). There were 11 cases (28.9%) of complications on the dorsum, four surface irregularity, five resorptions, and two cases of short nose deformity. CONCLUSIONS: One can augment the nasal dorsum significantly with crushed autologous costal cartilage. But considering high rate of recipient site complications, this method may better be used as an alternative technique when surgical situations are indicated. LEVEL OF EVIDENCE: 4 Laryngoscope, 131:E2181-E2187, 2021.

Numerical Simulations and In Situ Optical Microscopy Connecting Flow Pattern, Crystallization, and Thin-Film Properties for Organic Transistors with Superior Device-to-Device Uniformity.

Currently, due to the lack of precise control of flow behavior and the understanding of how it influences thin-film crystallization, strict tuning of thin-film properties during solution-based coating is difficult. In this work, a continuous-flow microfluidic-channel-based meniscus-guided coating (CoMiC) is introduced, which is a system that enables manipulation of flow patterns and analysis connecting flow pattern, crystallization, and thin-film properties. Continuous supply of a solution of an organic semiconductor with various flow patterns is generated using microfluidic channels. 3D numerical simulations and in situ microscopy allow the tracking of the flow pattern along its entire path (from within the microfluidic channel to near the liquid-solid boundary), and enable direct observation of thin-film crystallization process. In particular, the generation of chaotic flow results in unprecedented device-to-device uniformity, with coefficient of variation (CV) of 7.3% and average mobility of 2.04 cm2 V-1 s-1 in doped TIPS-pentacene. Furthermore, CV and average mobility of 9.6% and 11.4 cm2 V-1 s-1 are achieved, respectively, in a small molecule:polymer blend system. CoMiC can serve as a guideline for elucidating the relation between flow behavior, liquid-to-solid phase transition, and device performance, which has thus far been unknown.

Association Between Latency of Dermatomal Sensory-Evoked Potentials and Quantitative Radiologic Findings of Narrowing in Lumbar Spinal Stenosis.

OBJECTIVE: To identify the difference of quantitative radiologic stenosis between a normal latency group and an abnormal latency group, and to investigate the association of dermatomal somatosensory-evoked potential (DSEP) with magnetic resonance imaging (MRI) findings of narrowing in patients with lumbar spinal stenosis (LSS). METHODS: We retrospectively reviewed the clinical records and P40 latencies of L5 DSEP of 40 patients with unilateral symptoms of LSS at the L4-5 disc level. Quantitative assessments of stenosis in lumbar spine MRI were performed with measurements of the anteroposterior diameter (APD), cross-sectional area (CSA) of the dural sac, ligamentous interfacet distance (LID), CSA of the neural foramen (CSA-NF), and subarticular zone width. Analyses were conducted through comparisons of radiologic severity between the normal and abnormal latency groups and correlation between radiologic severity of stenosis and latency of DSEP in absolute (APD <10 mm) and relative (APD <13 mm) stenosis. RESULTS: The radiologic severities of lumbar stenosis were not significantly different between the normal and abnormal latency groups. In absolute and relative stenosis, latency showed a significant negative correlation with APD (r=-0.539, r=-0.426) and LID (r=-0.459, r=-0.494). In patients with relative stenosis, a weak significant positive correlation was found between latency and CSA-NF (r=0.371, p=0.048). LID was the only significant factor for latency (ß=-0.930, p=0.011). CONCLUSION: The normal and abnormal DSEP groups showed no significant differences inradiologic severity. The latency of DSEP had a negative correlation with the severity of central stenosis, and LID was an influencing factor.

Further effects of electromechanically assisted gait trainer (Exowalk®) in patients with chronic stroke: A randomized controlled trial.

OBJECTIVE: To assess the effect on walking ability of electromechanically assisted gait training with a gait trainer (Exowalk®) for patients with chronic stroke. DESIGN: Randomized controlled trial. SUBJECTS: Forty patients with hemiplegia after stroke. METHODS: Patients were randomly assigned to control and experimental groups. The control group underwent physical therapist-assisted gait training and the experimental group underwent electromechanically assisted gait training. Interventions were provided for 60 min, 5 days a week, for a period of 2 weeks. Primary outcome was change in Functional Ambulatory Category. Secondary outcomes were walking speed, walking capacity, leg muscle strength and balance. All outcomes were measured before and after the intervention. RESULTS: Although the Functional Ambulatory Category improved significantly after gait training in both groups, the change in Functional Ambulatory Category did not differ between groups. In both groups most secondary outcomes also improved after gait training, but the changes in secondary outcomes did not differ between groups. CONCLUSION: In patients with chronic stroke, walking improved after gait training with or without electromechanical assistance. Electromechanically assisted gait training was not superior to conventional physiotherapy.

Structural basis for carotenoid cleavage by an archaeal carotenoid dioxygenase.

Apocarotenoids are important signaling molecules generated from carotenoids through the action of carotenoid cleavage dioxygenases (CCDs). These enzymes have a remarkable ability to cleave carotenoids at specific alkene bonds while leaving chemically similar sites within the polyene intact. Although several bacterial and eukaryotic CCDs have been characterized, the long-standing goal of experimentally visualizing a CCD-carotenoid complex at high resolution to explain this exquisite regioselectivity remains unfulfilled. CCD genes are also present in some archaeal genomes, but the encoded enzymes remain uninvestigated. Here, we address this knowledge gap through analysis of a metazoan-like archaeal CCD from Candidatus Nitrosotalea devanaterra (NdCCD). NdCCD was active toward ß-apocarotenoids but did not cleave bicyclic carotenoids. It exhibited an unusual regiospecificity, cleaving apocarotenoids solely at the C14'-C13' alkene bond to produce ß-apo-14'-carotenals. The structure of NdCCD revealed a tapered active site cavity markedly different from the broad active site observed for the retinal-forming Synechocystis apocarotenoid oxygenase (SynACO) but similar to the vertebrate retinoid isomerase RPE65. The structure of NdCCD in complex with its apocarotenoid product demonstrated that the site of cleavage is defined by interactions along the substrate binding cleft as well as selective stabilization of reaction intermediates at the scissile alkene. These data on the molecular basis of CCD catalysis shed light on the origins of the varied catalytic activities found in metazoan CCDs, opening the possibility of modifying their activity through rational chemical or genetic approaches.